Thanks I managed to use it. I inserted a single loop with 3 edges(a triangle ) and succeded to make a triangle with hatch.

But pattern name is still a mistery.
I tried "EARTH", "ANSI31",... default pattern names,but nothing happens. However I can see that names in autocad when I click on my hatchobject, but it doesnt change the hatch style?!
I tried rotate and scale property too,they doesnt work either. Its always a 45 degree hatch.The solid property works fine.

wolfhergang: Can you post your code or the exact example data?I don't see how a hatch with one loop which contains one arc can form a closed, hatchable contour (unless the arc is in fact a full circle?).

in my implementation you "add" the entities to a container then you write the container to the file.the entity constructors are basically the same as the DL_Entity ones, but mine store the attributes, thats it.

the arc is supposed to be a full circle from 0 to 6.74 degrees but it doesnt render.